Sharepoint - Caml query builder Office 365 Sharepoint Online
The 2 popular CAML query tools are Strammit CamlViewer and U2U CAML Builder. They both say they're for 2007, but it's been proven they work fine for 2010 versions as well.
Edit: and the BIWUG CAML Designer works for O365 too.
Its an old question, but i will update for my finding..
there is SPCAMLQueryHelper
it has choice for office 365, i have tried it and its works :)
edit : in field username you should fill your email for o365 account, ex : [email protected]